This invention relates to cleaning compositions and more particularly to those compositions, hereinafter referred to as oxygen cleaning agents, which are employed in cleaning the surfaces of oxygen or oxygen-enriched liquid and gas generating, handling, transport and storage equipment used for life support, propulsion, and other functions and the parts and assemblies thereof, such as hoses, pipes, valves, tanks, flasks, connectors, pumps, regulators, face masks and the like. The invention also includes a method of manufacturing the cleaning composition and a method of cleaning using the cleaning composition.
The standards of the Department of Defense (DOD), National Aeronautical and Space Administration (NASA), National Fire Protection Agency (NFPA), American Society of Testing and Materials (ASTM) and Society of Automotive Engineers (SAE) all specify that the rigorous removal of organic and particulate contamination from oxygen and oxygen enriched handling equipment is absolutely necessary to prevent a fire hazard. Failure to thoroughly clean oxygen and oxygen enriched handling equipment will and has resulted in catastrophic fires. The DOD, NASA, NFPA, ASTM and SAE all have records of equipment damage and personnel injuries and death from fires caused by the failure to adequately clean oxygen and oxygen enriched handling equipment. Testing by NASA has demonstrated that, in the presence of an ignition source caused by the presence of particulate contamination or organic material, many metals will burn in an oxygen atmosphere; and that the rate of burning will be extremely fast. For example, ASTM document G94-88, "Standard Guide for Evaluating Metals for Oxygen Service" reports 6061 aluminum in 100% oxygen at 276 bars burned at an average propagation rate of 13.86 centimeters per second and 316 stainless steel in 100% oxygen at 276 bars burned at an average propagation rate of 1.24 centimeters per second. NASA has high-speed video footage of a 690 bars rated valve operating with 276 bars gaseous oxygen as it fails due to particulate contamination. The conflagration penetrated and expanded beyond a 7.62 centimeter thick stainless steel valve in 0.25 seconds. Accompanying the fire hazard is a toxicity hazard associated with oxygen and oxygen-enriched handling equipment used in providing life support functions. The organizations previously referred to all have reports of personnel injury and death from toxic residue remaining in life-support equipment that was cleaned with a cleaning agent which was inadequate, either because it failed to remove toxic contaminants or because it contained toxic contaminants itself. As an example, the use of chlorinated hydrocarbon solvents is prohibited in underwater diving life support equipment because these compounds dechlorinate in carbon dioxide scrubbers, forming highly toxic and flammable dichloroacetylene.
The requirements for oxygen cleaning agents include the capability of removing common hydrocarbon soils such as lubricating oils and greases, since the presence of these soils represents an extreme fire hazard. Further, oxygen cleaning agents must be capable of removing particulate contamination, since the presence of excessive particulate contamination provides a potential ignition source in oxygen and oxygen-enriched handling equipment. Further, oxygen cleaning agents must be capable of removing halogenated lubricants approved for use with oxygen storage and delivery equipment. Although halogenated lubricants are used in oxygen-enriched handling equipment because they are not flammable, the failure to remove these lubricants during cleaning provides a mechanism for trapping particulate and/or hydrocarbon contamination. Further, the oxygen cleaning agent itself must be non-flammable in a gaseous or liquid oxygen environment so as not to present a fire hazard in the event the cleaner is not completely removed. Further, the oxygen cleaning agent itself must be either non-toxic or of an acceptable low level of toxicity as determined by a medical evaluation (such as trichlorotrifluoroethane solvent (also identified as CFC-113)) in the event the cleaner is not completely removed during the cleaning process. Further, the oxygen cleaning agent must be capable of being analyzed for residual total hydrocarbon contamination with a sensitivity of at least 1 part per million (ppm) to permit accurate, certifiable verification of hydrocarbon cleanliness. Finally, Department of Defense (DOD), National Aeronautical and Space Administration (NASA), and various commercial standards require oxygen-enriched handling equipment to be certified hydrocarbon clean. The DOD standard (MIL-STD-1330C) certifies hydrocarbon cleanliness when the effluent cleaning agent, that is, the cleaning agent following its use in cleaning the oxygen enriched handling equipment, measures less than 5 ppm total hydrocarbon contamination. A conversion factor is applied to convert the DOD standard to the NASA hydrocarbon cleanliness standard of 1 milligram per square foot.
The two principal existing oxygen cleaning agents are trichlorotrifluoroethane solvent (also identified as CFC-113) and tribasic sodium phosphate solution (also identified as TSP). CFC-113 is an ozone depleting substance, and a replacement will become necessary because its production is banned after Dec. 31, 1995. TSP has the disadvantage that it is a hazardous environmental waste. Further, TSP is corrosive to amphoteric metals such as aluminum. Further, TSP is of marginal effectiveness in removing the halogenated lubricants which can trap particulate and hydrocarbon contaminants. Further, TSP must be applied at relatively high temperatures in the range of 71.1.degree. C. to 87.8.degree. C. Further, at temperatures below the above-noted range, TSP precipitates leaving harmful deposits. Further, TSP leaves a phosphate layer on the surface being cleaned which may deleteriously affect the finish (smoothness) of that surface even after rinsing with water. Finally, the use of TSP as a cleaner requires extensive rinsing to prevent the formation of hard phosphate residues which are not readily soluble in water and which are detrimental to critical components.
In addition, there are numerous aqueous or solvent based biodegradable cleaners available which claim to have oxygen system cleaning capabilities. However, these cleaners contain hydrocarbon derivative components (such as organic surfactants) and thus have the disadvantages associated with hydrocarbons previously noted. Specifically, they have the fire hazard associated therewith, a potential toxicity hazard in life-support systems and an inability to analyze the effluent cleaning agent for residual total hydrocarbon contamination with a sensitivity of at least 1 part per million (ppm) to permit accurate, certifiable verification of hydrocarbon cleanliness. Finally, alternate chlorinated solvents such as perchloroethylene and methylene chloride are unusable in any life-support equipment because these solvents are highly toxic, having been identified as suspected human carcinogens.